The present invention relates to a device of the type stated in the introduction to claim 1, and a method of the type which is stated in the introduction to claim 13. The invention concerns particularly the controlling of an industrial machine, for example a ground-leveling machine, crane, dredger or the like.
During road construction or the leveling of ground, for example for buildings, parks or playgrounds, vehicle displays or the like, ground preparation machines are used which are to give a predetermined topography to the piece of ground through, on one hand digging and on the other hand piling up material.
It is important in this connection that the working tools on the machines which are used can be accurately controlled to the exact right working level in the intended section. The control should preferably even be able to be remote-controlled automatically so that the desired topography in the right position inside a section should be able to be written into a computer programme and information concerning suitable processing should be able to be given continuously and automatically to the driver of the vehicle. It should also, in the cases where it is possible, be able to have automatic controlling of the machines in order to perform certain work completely automatically.
This implies that for ground-working equipment one needs to keep track of the exact position in space of the working tools"" positions in space, the angular position in both horizontal and vertical directions and their working directions.
U.S. Pat. No. 4,807,131 (Clegg Engineering) describes a ground preparing system with the use of an instrument with a horizontal plane-identifying rotating sweeping beam, and a height indicator placed on a ground-preparing machine, for hitting by the sweeping beam. The height indicator is placed directly onto the working tool of the machine, for example on the blade of an excavator. Furthermore, a separate position generator can be placed on the machine and cooperate with an electronic distance: measuring instrument in order to give the position of the machine in the region which is to be treated. The signals from the different above-mentioned indicators are fed to a computer, which is given information on the desired topography of the region of ground via predetermnined, composite data, and which compiles measuring values and gives indication for controlling the working tool of the machine.
To determine the orientation and inclination via machine movements is a slow method. Likewise, position- and height-determination with the aid of GPS-technique or with electronic angular and distance measuring often is not sufficiently fast in order to be able to measure the position and, above all, the height with sufficient accuracy during fast displacements.
One object of the invention is to provide a control resp. a control indication for a ground-preparing machine, which makes possible adequate control of the machine with so few as possible measuring units placed outside the machine.
Yet another object is to provide an instantaneous, continuous and correct position and direction indication of a ground-preparing machine during work, even during fast movements.
Another object of the invention is to produce controlling of a ground-preparing machine, where that which is important is the indication of working position and working direction of the working part of the machine tools but where the influence of the vibrations of the working part, unfavourable environment, obscured positions etc. are removed.
A further object of the invention is to provide a direct position-determining and an automatic following of the working portion of the machine""s working part during the working operation.
A further object of the invention is to provide a flexible system which is usable for measuring of the instantaneous working position and the working direction for different types of working machines, e.g. ground-preparing machines, digging machines, cranes, etc.
The above mentioned objects are obtained with a device which has the features stated in the characterizing part of claim 1. Further characteristics and developments are stated in the other claims.
The invention is characterized in that the position- and orientation-determining apparatus can comprise, on one hand, a relatively slow, accurate determining device, which at time intervals accurately measures the current position and orientation of the machine, and on the other hand a fast determining device, which reacts on position and/or orientation changes in order to calculate and update the calculation between said time intervals. This fast determination device in this case only has to be stable for short periods of time because a slow drift is corrected through updating from the slower device.
The relatively slow, accurate position and orientation determination can take place with the help of a stationary measuring station, for example a geodesic instrument with automatic target-following or a radio navigation system, for example GPS (Global Positioning System) placed in the vicinity of the working machine for position-determining in cooperation with the detector device. The inclination can also be determined e.g. by inclinometers and the orientation around the vertical axis e.g. by compass or by a north-seeking gyro.
The short time-period-stable determining device can thereby comprise an accelerometer device on the machine for measuring the acceleration of the machine in at least one direction, preferably in several mutually different directions, whereby the calculation unit double-integrates the indicated acceleration or accelerations and updates the latest calculated result of the position in the fixed coordinate system.
When a quick determination of a change of orientation is needed. preferably a further accelerometer or a gyro is used for each axis around which rotation is to be determined. The signals from these sensors are used, after suitable integration and conversion from the coordinate system of the machine to a fixed coordinate system, to update the position-determninations for the machine in the fixed coordinate system. A suitable way of putting together the information from the slow and the fast sensors in an optimal manner is to use Kalmann filtering.
Preferably, measuring and calculation are continuously performed at intervals while the machine is in operation. The calculating unit calculates after each measuring the position, and possibly the direction of working and the speed of working, of the working part of the tool, using the latest and earlier calculation results for the position. The calculating unit can also use earlier calculation results in order to predict the probable placement, orientation, direction of working and speed, a certain time in advance for the working part of the working machine.
By the invention a measuring system has been produced which is easy to use and which furthermore is relatively cheap. Already existing stations for measuring a region can be used for controlling the working machines. This means that special equipment for the stations does not need to be bought or transported to the working place, especially for use with the invention. However, extra equipment is needed on the working machine.